Artificial tooth



ocrn 27, 1942. s MYERs-N 'l 2,300,305

ARTIFIGIAL TOOTH Qriginal Filed Harsh 15, 1940 Patentedv ocr. 27, 1942 Y2,300,305 ARTIFICIAL TOTH Simon Myerson, Brookline, Mass.

Original application March 15, 1940, Serial No.

324,127. Divided and this application September 27, 1941, Serial No.412,574v

11 Claims. (Cl. 32-8) This invention pertains to articial teeth and lrelates more particularly to improvements designed to impart anappearance more closely Y simulating that of natural teeth than hasheretofore been done, the present application being a division of mycopending application Serial No. 324,127, led March 15, 1940.

Attempts have previously been made by teeth manufacturers and dentiststo make artificial teeth resemble natural teeth in appearance, butdespite the most artistic carving and the application of stains andglaze by. the dentist, the articial tooth is readily distinguishablefrom the normal tooth, at least by experienced persons.

Apparently most previous experiments designedto improve the visualappearance of artificial teeth have been without due regard to the factthat when in use the tooth is viewed against the dark backgroundafforded by the oral cavity, and that the effect of light striking thetooth and being partially reflected therefrom is greatly modified by thepresence of this dark background, Failing to recognize this fact, muchof the prior experiment and practice hasbeen concerned with the use ofcolored materials and the application of stains or the like in theeffort to obtain the Ipeculiar shadowy effec't observed in natural teethunder'varying light conditions, but whereas colored material or stainmay be effective for the intended purpose under some A light conditionsthey frequently fail utterly to Vit-'vforms portions of both the labialand lingual surface of the tooth and Vextends aV substantial material ofthe transparent cap.`v Thus the darkness of theoral cavity is effectivenot only at :the extreme incisal edge but also for a substantialdistance (but with diminishing intensity) away from said edge, and thisI believe is responsible in large measure for the characteristicappearance of natural teeth as contrasted with that of articial teethmade in accordance with prior practice.

The principal object of the present invention -is to provide artificialteeth which as nearly as possible simulate theA appearance of naturalattained by the novel arrangement of the transparent' enamel and therelatively opaque body portion, as above described. VTo 'this end Icause the body portion to taper downward but to terminate short of theincisal edge, and.cause the enamel layer which covers the labial surfaceof the tooth to merge with .an incisal mass whichreceives and is fusedwith the tapered en d of the body portion and which forms the incisaledge and also the lateral edgesl of the tooth. The transparent materialis so blended with the more opaque body material that the finished toothhas a margin, including the incisal edge, which is preferably ofsubstantially complete transparency, that is to say, it so freely admitsthe passage of light that objects may be seen with well defined outlinesthrough the substance of the tooth at its incisal portion, the body andgingival portions being as opaque as may be de.- sired.

' I also construct the'tooth oi' a tooth facing so that it may bemanufactured in finished form and by mass production methods.

The result of the improved construction is lthat when the tooth is inuse and viewed againstthe dark oral cavity, the incisal portion of, thetooth appears to have a dark bluish shadowy fringe, closely simulatingthe natural tooth, such appearance varying withdifrerentught condamnant.

, changes in perspective as it does in 'a natural distance downwardlybeyond the relativelyA opaque body portion ofthe tooth, no'one, so

far as I am aware, has heretofore recognized 'l the fact that this is animportant factor in respect to the optical appearance ofthe naturaltooth. Moreover, in the natural tooth, the opaque body portion usuallytapers in thickness fective forward reflection of light gradually di-Aduction methods, possess the lack of uniformity of natural teeth. Y

Other objects and `advantages of the present 4invention will be mademanifest in the following inore detailed description and by reference tominishes to the point where it merges with the the accompanyingdrawings, vvherinrr` Fig. 1 is a side elevation of a tooth, for examplean anterior tooth, embodying the present invention; e

, Fig. 2 is afront or labial view of the tooth of Fig. 3 is a verticalsection on the line 3-3 of Fig. 2;

Fig. 4 is a transverse section on the line 4 4 of Fig.,3; f

Fig. 5 is a vertical section substantially on the line 5-5 of Fig. 3;and l Fig. 6 is a section similar to Fig. 3, showing a still furthermodification.

With reference to the following description of the improved toothstructure, it may first be stated that the improved tooth may be made insubstantial accordance with usual methods employed in making .artificialteeth, including the packing of suitable plastic slip material into thecavities ofcomplemental mould members; the closing of the mould membersand subjecting them to pressure and heat; and the subsequent removal ofthe green" teeth from the mould and the firing of the teeth (assumingthat they are of ceramic material) at a temperature such as to harden,and to some extent at least, fuse the material of which the tooth iscomposed.

While as above pointed out it is'the principal object of the inventionto provide artificial teeth which, when in use, are substantiallyindistinguishable in appearance from. natural teeth, it is,

of course, obvious that teeth made b'y a moulding overlying and beingfused to the labial surface of the body portion.

Inspection of Fig. 3 shows that the surface or .zone of contactI betweenthe forward, upwardly directed cusp of enamel and the labial surface ofthe body portion. gradually recedes from said labial surface I of thebody portion concomitantly with the approach of said contact surface orzone toward the incisal edge. In other words, the frontftorear thicknessof the cusp increases downwardly, and this gradual increase in thicknessof enamel, together with the downward and rearward slope of the labialsurface of the spur I, results in a progressive diminution of the amountof incident light which is reected forwardly from said labial surface ofthe body portion (including the spur Ia) so that the color tone impartedby the body material to thetooth becomes less and less pronounced assaid horizontal plane is approached.

As illustrated in Fig. 3, a secondv or rear extension or cusp, integralwith the enamel mass,

process are not natural teeth, either in respect l to'the material ofwhich they are constructed or in actual internal structure; nor are theysubject to decay, disease or pain;

Referring toFigs. 1 to 5 of the drawing, which illustrate certain broadaspects of the invention, the numeral I designates the body portion of atooth, suchrbodyportion being formed from a slip material designed toproduce a body of a substantial degree of opacity, it being understoodthat the slip material forming the body portion may be tinted asdesired. so as accurately to simulate the color of the body portion of anatural' tooth.

The body portion I` preferably has embedded therein a suitableanchorage, for example, a metal part 2, which receives a pin 2* solderedor otherwise secured to the anchorage, and by means of which the toothmay be mounted on a support, for example, a plate or bridge.

The body portion I has the gingival surface 3,

the labial surface 4 and the lingual or pin-bearing surface 5, whichextends down from the girigival surface to the-usual plate-limiting bossor shoulders and preferably tapers downwardly at its lower part to forma spur or tongue-like portion I the lower end of which is substantiallyspaced from the incisal edge 9 ofthe finished tooth. Y

Below the body portion is an incisal mass 6 of enamel. The lower marginof this mass is shaped to form the incisal edge 9 which is of smallradius (in vertical section) similar to that of the natural tooth. Theincisal edge is vertically spaced from the horizontal plane ofthe'lowestpart of the body portion across the entire width of the tooth,and the incisal mass tapers downwardly in front-to-rear thickness (Fig.3) from said plane.v The incisal7 mass has an integral, forwardportion,extending upwardly) above said horizontal plane.' said upward extensionbeing i diere shownnasgtapering (as the toothis viewed in vertical midsection, Fig. 3)toform a cusp and 'surface of the body portion.

extends upwardly from said horizontal plane so as to overlie and isfused with the Alower lingual Said rear cusp preferably extends upsubstantially to the usual plate-limiting boss or shoulder S of thetooth.

The exposed rear surfaces of the enamel massproper. and its rear cuspmerge smoothly, and collectively form the concave lingual surface 8 ofthe tooth, while the exposed forward surface of the enamel mass properand the forward cusp merge smoothly, and collectively form the lowerportion at least of the convex labial surface 1 of the tooth.

The incisal mass 6 also comprises integral lateral extensions 62. and 6b(Figs. 2 and 5) which extend upwardly at opposite sides of the spur I*of the body portion, the edgesof these extensions SLand 6b mergingsmoothly with the lateral edges Im and In of the body portion. Thus, asherein specifically illustrated (Figs. 3 and 4), the incisalmassjform's'an inverted cap or crown having a downwardly directed cavityconstituting in effect a socket for the reception of the spur I, the

'latter being embedded in and fused with the material forming the wallsof such socket.

As here shown the spur I* terminates at a substantial distance above theincisal edge 9 of the tooth. This distance is such as to permit light topass so freely'through the entire widthof'the incisal portion of thetooth (except as such pass'- age may be locally obstructed by stria orother defect-simulating elements embedded in the enamel mass)- Vas toimpart to the tooth the appearance when in use of having a dark shadowyfringe of progressively deepening tone, thereby to simulate naturalteeth, as more fully described hereinafter. This distance is at leastapproxi'- mately one-third the horizontal distance between the labialsurface 4 andthepingbearing surface 5ftlatist6'say atleast approximatelyone-third of the maximum front-to-rear .horizontal thickness of thetooth at its upper portion. Since such front-to-rear thickness in usualand normal types ofcommercial articial teeth is commonly in theneighborhood of three-sixteenths of an inch (at the upper portion of thetooth) the depth of the incisal mass in accordance with the ratio abovesuggested would usually be of the order of onesixteenth of an inch ormore. y

When, in the vlappended claims, the distance between the lower end ofthe spur I* and theincisalv edge is referred to as a "substantialdistance, the word substantial is hereby intended and is to be construedas indicative of a distance such as defined by the above specifieddimensional relationships. The enamel-forming slip used in making theincisal cap 6 is such that when the tooth is completed the ca'ptransmits light much more readily than'does the material of the bodyportion I. In fact', the cap is transparent to the extent that theoutlines of an object may be seen through the substance of the tooth atthe incisal portion of the latter, the tooth in this respect closelysimulating a usual natural tooth.

- When a tooth constructed as above described against the darkbackground of the oral cavity,

light is reflected forwardly from the labial surface 4 of the bodyportion I, the latter being substantially opaque and usually of alightcolor,

.of the cap 6 as above described, not only to obtain a mechanicaladvantage in effecting a strong union between the body portion and thecap, but

for the further reason that the gradually taperl ing spur Ia with itsforwardly convex labial surface results in a gradual lessening of the-amount of light which is reected forwardly with a corresponding changein appearance froml the relatively light appearing/upper portion of thetooth down toward the dark incisal edge portion; thus further simulatingthe appearance of the natural tooth in which the opacity graduallyincreases from the incisal edge toward the gingival surface and likewiseinwardly from the lateral edges toward the center of the tooth.

While as illustrated in Fig. 3 the enamel forming the cap 6 terminatesabout midway the height of the tooth, it is contemplated that the enamellayer might be extended up even as far as the gingival surface. Thus, asshown in Fig. 6, where the tooth is otherwise like that in Fig. 3, thematerial forming the cap 6 is shown as extending up in a thin layer BXcovering and protecting the labial face of the body portion I. With suchan arrangement, if the enamel layer 6X be colorless but substantiallytransparent, the color of the body material will show through thisenamel layer without substantial change except that the enamel layerimparts a bone-like or ivory luster to the entire labial surface of thetooth.

As disclosed in my Patent N o. 2,202,713 issued May 28, 1941, the toothmay, if desired, be constructed so as further to simulate a naturaltooth by the inclusion of narrow streaks or areas of a color orappearance which visually contrasts with that of the enamel andsimulates the stains, dead spots, or striae common in natural teeth. l

In the above description, when reference has been made to the upper orlower part of the tooth, it is to be understood that these and similardirectional terms are used merely for convenience in description andwith reference to the drawings, and without limiting intent.

Obviously other 'modifications and equivalent Iarrangements may beemployed, and it is to be understood that all such modifications,substitutions of material, etc., as fall within the scope o f` theappended claims, are to be regarded as a part of the present invention.

incisal portion, said mass of enamel having an i upward extensionoverlying the lower part at least of the labial surface of the bodyportion, said mass of transparent enamel extending ver tically downbelow the lowest point of the body portion to a distance which at leastapproximates one-third of the maximum horizontal distance between thelabial and lingual surfaces of that part of the tooth which is above theplate-limiting shoulder, thereby imparting a dark appearance to theincisal portion of the tooth when the tooth is viewed against the darkbackground of the `oral cavity.

2. An artificial tooth having a downwardly and rearwardly slopinggingival surface, a pin-bearing surface and a plate-limiting shoulder,said tooth comprising a body portion of relatively opaque material andbeing v'provided with pins for attaching the tooth to a support, and anincisal portion of material of such transparency that the outline of anobject may be seen through the substance of the tooth at said incisalportion,

said portions meeting and merging in a contactJ zone whose nearestapproach to the incisal edge is at a distance from the 'latter which atleast approximates one-third the maximum horizontal distance between thelabial and pin-bearing surfaces of the tooth, said contact zonegradually receding from the labial face and from the lateral .edges ofthe tooth as it approaches the incisal edge whereby the tooth has arelatively transparent light-transmitting fringe of substantial depth.the transparency of which gradually diminishes inwardly away from saided'ges.

3. A moulded artificial tooth constituting an article of manufacture andsale formed from mouldable material and `devoid of roots, pulpupwardlyabove said horizontal plane and overlying and being fused to the labialsurface of the lower part at least ofthe body portion, characlferized inthat the enamelmass is of substantially complete transparency and whoseminimum depth below said horizontal plane at least approximatesone-third of the maximum front-torear thickness of the upper portion ofthe tooth whereby a dark shadowy appearance is imparted toxthe toothwhen the latter the darkness of the oral cavit 4. As an article ofmanufacture, a moulded ,is viewed against artificial tooth including a-body p ortion of relayfront-to-rear thickness pering downwardly fromsaid lplane such transparency that the outline of an objectl tivelyopaque material and a mass of substantially transparent enamel below thebody portion, said mass of enamel tapering downwardly in from thehorizontal plane of the lowest part of the body portion, ,the lowermargin of said enamel mass being shaped to form an incisal edge of smallradius, said edge being spaced vertically a substantial distance belowsaid plane across the entire width of the tooth, said enamel mass havingintegral portions extendingA upwardly above said horizontal plane at thefront and rear sides respectively of said extensions overlying and beingfused to the lower portions at least of the labial land lingual surfacesof the body portion, the exposed surfaces of said upward extensionsmerging smoothly with the front and rear surfaces of the enamel massproper thus providing smoothly curved convex and concave labial andlingual tooth surfaces, said latter surfaces converging toward theincisal edge, the depth of the incisal mass from said horizontal planeto the incisal edge exceeding the thickness of the enamel at any pointabove said horizontal plane as measured from the outer sur-'- face ofthe enamel in a direction normal to the surface of the body portion, itsdepth and trans.

parency being such as to impart a dark shadowy appearance to the incisalportion of the tooth when the latter is viewed against the darkbackground of the oral cavity.

5. As an article of manufacture and sale, an artificial tooth, mouldedfrom plastic material and-devoid oflroots, pulp-cavity or nerves, saidtooth comprising a body portion which is relatively opaque and anincisal portion of substantially transparent material, said portionsbeing so const'ructed and arranged that at the vertical mid-plane of thetooth 'said portions meet in a rearwardly and downwardly sloping line ofcontact whose distance from the labial 'surface of the toothprogressively increases and whose lowest point is a substantial distanceabove the incisal edge of the tooth, the incisal. -portion beingthickest horizontally in the horizontal plane of the lower end of saidline of contact and tapering downwardly from said horizontal plane, saidtaincisal portion being so transparent that the outlines of an objectmay be observed through its substance and the minimum depth of saidtransparent incisal mass below the lowest part ofthe body portion beingsuch that when the tooth isviewed against the dark background ofthe.oral cavity it appears to have a dark shadowy incisal fringe acrossits entire width.

6. As an article of manufacture and sale, an artificial tooth, formedfrom mouldable material,

devoid of' roots, pulp-cavity or nerves", said tooth comprising a bodyportion which 'is relatively opaque and an enamel portion ofsubstantially transparent material, the enamel forming ,the majorportion at least of the labial face of the tooth and constituting theincisal edge of the tooth across the entire width of the latter, thelabial surface and 'lateral edges of said opaque body kportionprogressively receding from the exposed labial face and from the exposedlateral edges respectively of the tooth as they approach the incisaledge," the enamel portion comprising an incisal mass 'which ishorizontally thickest yfrom front to rear inthe plane of the lowestpoint of the body portion and which tapers and which is of may be seenthrough it, the lowest point of the body portion being spaced such asubstantial distance from the incisal edge across the entire width ofthe tooth as to permit the transmission of light through said incisalmass from front to the tooth,

rear unobscured by any part of said body portion, thereby imparting adark shadowy appearance to the incisal portion of the tooth whenit isviewed against a dark background.

'1. An artiiicial tooth comprising a body portion of relatively opaquematerial and constituting the major part .of the tooth, and an incisalportion of a relatively transparent enamel, the lower part of the bodyportion tapering downwardly, at least in front-to-rear section, and theincisal portion terminating at the incisal edge, characterized in thatthe incisal portion is substantially sagittate` in verticalfront-to-rear section, having upper labial and lingual'cusps, theincisal portion extending below the lower end of the body portion to adistance substantially exceeding the maximum front-to-rear thickness ofits labial cusp, whereby when the tooth is viewed against the backgroundof the oral cavity its incisal portion appears of gradually increasingdarkness toward its incisal edge. I

8. An'artiiicial tooth comprising a body portion of relatively .opaquematerial which constitutes the major part of the tooth and whichterminates short of the incisal edge ofthe tooth, a layer of material ofa different degree ofopacity overlying that part of the labial surfaceof the body portion which is remote from the gingiyal surface of thetooth, and a cap of relatively transparent material-which embraceslthelower end of the body portion with its overlying layer of material, thecap terminating in an incisal edge and having labial and lingual faceswhich' merge at said edge, the `cap including a labial portion whichextends upwardly a substantial tion of the cap whereby, when the toothis viewed against the dark background of the oral cavity, the lower partof the tooth appears darker than the gingival portion of the tooth.

- 9. An artificial tooth of the kind having a body portion of relativelyopaque ceramic material which constitutes the major part of the toothand enamel forming the incisal edge of' the tooth, characterized in thatthe edge-forming enamel is an .integral part of a mass of substantiallycolorless enamel which is relatively more transparent than the materialof the body of the tooth and whichhas an upward extension overlying thelower part atleast of the labial surface of. the body portion,` saidmass of enamel extending vertically down below the lowest point of thebody portion to a distance exceeding one-third of the maximum horizontaldistance between the labial and lingual surfaces of the tooth, therebyimparting a dark appearance to the incisal portion of the tooth when thetooth is viewed against the dark background of the oral cavity.

10. An artificial tooth having a body portion of relatively opaquematerial, said body portion being provided with means for attaching thetooth to a support', and an incisal portion of relatively transparentmaterial, said portions meeting'and merging in a contact zone whosenearest approach-to the incisal edge is at a distance from the latterexceeding one-third the maximum horizontal distance between the labialand lingual surfaces of the tooth, said contact zone gradually recedingfrom the labial face and from the lateral edges of the tooth whileconcomitantly approaching the incisal edge whereby the tooth has arelatively transparent lighttransmitting fringe of substantial depth,the transparency of which gradually diminishes inwardly away from saidedges.

11. An articial tooth having a body portion of relatively opaquematerial which constitutes the major part of the tooth and a mass ofrelatively transparent enamel which forms the incisal edge, the bodyportion tapering downwardly to form a spur whose lcwer end issubstantially spaced from the incisal edge of the finished tooth,

the mass of enamel having a socket cavity in which the spur of the bodyportion is seated and a layer of ceramic material having a diierentvisual appearance from that of the body of the tooth disposed againstthe labial surface of said spur, said -layer having a thin upwardlydirected extension overlying the upper part of the body portion of thetooth and extending substantially to the gingival surface, the mass. ofenamel which forms the incisal'edge also having a thin upwardly directedextension which overlies the extension of the ceramic layer and whichalso terminates substantially at the gingival surface of the tooth.

SIMON MYERSON.

